Coma Via Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coma Via Observatory clear sky chart from 2005-11-05 to 2017-12-02.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
71%
15842
30%
47787
27%
15808
74%
15808
46%
24582

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
59%
717
22%
2497
21%
716
65%
716
34%
1348
January16th to endNight
53%
768
26%
2489
22%
768
61%
768
32%
1445
February1st to 15thNight
53%
700
25%
2112
21%
700
60%
700
31%
1289
February16th to endNight
54%
632
22%
1895
22%
632
58%
632
29%
1192
March1st to 15thNight
64%
720
19%
2160
21%
720
66%
720
35%
1264
March16th to endNight
65%
768
22%
1991
16%
768
68%
768
40%
1202
April1st to 15thNight
60%
719
24%
1799
14%
719
63%
719
39%
1115
April16th to endNight
63%
720
26%
1800
14%
720
66%
720
50%
999
May1st to 15thNight
71%
608
29%
1688
21%
608
73%
608
55%
838
May16th to endNight
65%
510
29%
1634
25%
510
68%
510
46%
781
June1st to 15thNight
81%
360
33%
1440
38%
360
85%
360
52%
554
June16th to endNight
94%
360
41%
1440
51%
360
96%
360
80%
420
July1st to 15thNight
93%
340
34%
1360
43%
340
93%
340
65%
470
July16th to endNight
91%
479
39%
1512
40%
450
91%
450
63%
608
August1st to 15thNight
92%
717
38%
1790
25%
713
92%
713
82%
789
August16th to endNight
93%
764
45%
1910
29%
764
94%
764
81%
857
September1st to 15thNight
92%
720
43%
1800
32%
720
93%
720
77%
829
September16th to endNight
86%
716
46%
1980
41%
716
90%
716
74%
843
October1st to 15thNight
77%
720
33%
2058
32%
720
81%
720
56%
1004
October16th to endNight
78%
768
38%
2331
41%
768
82%
768
51%
1141
November1st to 15thNight
71%
760
28%
2470
30%
760
75%
760
43%
1249
November16th to endNight
66%
780
28%
2535
29%
780
70%
780
38%
1346
December1st to 15thNight
60%
728
25%
2408
22%
728
66%
728
33%
1366
December16th to endNight
49%
768
23%
2688
21%
768
56%
768
25%
1633

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
6%312212335%65%
48673
Night
7%312212235%65%
47968
TransparencyDay
22%47%19%27%17%
48355
Night
23%48%21%26%15%
47788
SeeingDay
9%10%29%36%10%3
6126
Night
9%213%35%33%6%
15852

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
11%6%1332345%7%50%
1438
16th to endDay
14%6%2432345%6%46%
1734
February1st to 15thDay
14%7%23312348%47%
1751
16th to endDay
17%8%245%23345%41%
1579
March1st to 15thDay
11%8%1332445%7%47%
1800
16th to endDay
11%6%24313436%50%
2232
April1st to 15thDay
12%6%24412435%51%
2149
16th to endDay
8%412323346%57%
2160
May1st to 15thDay
5%2221225%7%67%
2262
16th to endDay
6%212213346%65%
2477
June1st to 15thDay
321112336%73%
2520
16th to endDay
1112386%
2520
July1st to 15thDay
111112235%78%
2520
16th to endDay
11121223477%
2550
August1st to 15thDay
111111286%
2160
16th to endDay
111121385%
2292
September1st to 15thDay
1111112384%
2160
16th to endDay
1111122384%
1980
October1st to 15thDay
5%22212335%69%
1901
16th to endDay
5%313223345%65%
1893
November1st to 15thDay
6%5%13313335%61%
1719
16th to endDay
8%5%13423247%56%
1755
December1st to 15thDay
11%5%1331335%8%51%
1585
16th to endDay
16%7%24313347%45%
1536
January1st to 15thNight
12%31331235%6%54%
2497
16th to endNight
13%5%23323347%51%
2489
February1st to 15thNight
13%7%24222348%48%
2101
16th to endNight
18%5%23222347%47%
1895
March1st to 15thNight
9%42332445%7%53%
2160
16th to endNight
11%412223448%54%
1991
April1st to 15thNight
12%412213436%57%
1799
16th to endNight
8%31222136%66%
1800
May1st to 15thNight
5%2112236%72%
1688
16th to endNight
8%222223470%
1633
June1st to 15thNight
411111235%76%
1440
16th to endNight
11290%
1440
July1st to 15thNight
1111222481%
1440
16th to endNight
11112112381%
1615
August1st to 15thNight
11111388%
1800
16th to endNight
1122188%
1910
September1st to 15thNight
1111122384%
1800
16th to endNight
111222383%
1980
October1st to 15thNight
5%1221323472%
2058
16th to endNight
421221243470%
2331
November1st to 15thNight
6%412312246%63%
2470
16th to endNight
7%423312348%57%
2535
December1st to 15thNight
11%413323346%53%
2408
16th to endNight
15%6%24323346%47%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
31%6%9%22%21%9%
1438
16th to endDay
39%5%9%16%17%11%
1734
February1st to 15thDay
36%410%22%18%7%
1751
16th to endDay
47%46%24%15%1
1579
March1st to 15thDay
36%6%12%20%17%6%
1800
16th to endDay
36%6%14%23%16%2
2232
April1st to 15thDay
36%5%10%26%16%4
2149
16th to endDay
27%5%12%27%23%3
2160
May1st to 15thDay
19%410%26%33%4
2262
16th to endDay
21%5%6%34%27%3
2480
June1st to 15thDay
14%5%7%19%34%17%
2520
16th to endDay
6%218%44%35%
2520
July1st to 15thDay
11%3211%25%46%
2371
16th to endDay
13%3313%30%36%
2392
August1st to 15thDay
6%2110%38%40%
2146
16th to endDay
7%2110%44%34%
2292
September1st to 15thDay
8%2313%36%34%
2160
16th to endDay
7%2123%42%22%
1980
October1st to 15thDay
19%35%21%28%20%
1901
16th to endDay
22%5%420%26%21%
1893
November1st to 15thDay
26%5%8%21%26%11%
1719
16th to endDay
29%49%20%25%10%
1755
December1st to 15thDay
30%6%12%20%21%9%
1585
16th to endDay
39%5%13%20%14%7%
1536
January1st to 15thNight
30%49%24%21%8%
2497
16th to endNight
33%5%9%17%18%14%
2489
February1st to 15thNight
36%48%21%21%7%
2112
16th to endNight
38%6%12%23%17%2
1895
March1st to 15thNight
31%6%14%21%19%6%
2160
16th to endNight
29%6%17%28%15%2
1991
April1st to 15thNight
30%6%12%29%15%5%
1799
16th to endNight
22%416%30%23%3
1800
May1st to 15thNight
16%411%29%32%4
1689
16th to endNight
20%48%29%33%3
1634
June1st to 15thNight
14%38%22%33%16%
1440
16th to endNight
41211%47%32%
1440
July1st to 15thNight
9%2312%28%43%
1360
16th to endNight
12%2414%26%40%
1512
August1st to 15thNight
6%1212%37%39%
1790
16th to endNight
6%1112%47%29%
1910
September1st to 15thNight
7%2314%34%36%
1800
16th to endNight
8%1325%37%23%
1980
October1st to 15thNight
17%35%23%29%20%
2058
16th to endNight
18%5%5%22%26%21%
2331
November1st to 15thNight
24%410%19%27%14%
2470
16th to endNight
27%49%19%25%12%
2535
December1st to 15thNight
32%5%10%21%23%7%
2408
16th to endNight
39%6%11%19%15%7%
2688

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
45%30%12%10%1
66
16th to endDay
20%6%29%27%13%2
257
February1st to 15thDay
20%9%27%29%10%2
266
16th to endDay
23%9%33%25%7%
238
March1st to 15thDay
17%11%30%29%10%1
270
16th to endDay
15%18%32%25%6%1
288
April1st to 15thDay
18%21%31%20%5%1
269
16th to endDay
8%30%33%23%31
270
May1st to 15thDay
10%17%33%28%8%1
288
16th to endDay
10%17%30%32%6%3
330
June1st to 15thDay
314%33%35%10%2
315
16th to endDay
17%27%43%14%6%
315
July1st to 15thDay
2226%47%15%5%
305
16th to endDay
2215%59%14%6%
327
August1st to 15thDay
2334%44%9%5%
315
16th to endDay
129%51%10%6%
332
September1st to 15thDay
2430%46%11%4
315
16th to endDay
29%35%40%11%
315
October1st to 15thDay
411%39%36%6%1
315
16th to endDay
8%8%26%37%16%1
309
November1st to 15thDay
6%5%24%32%25%5%
135
16th to endDay
15%9%13%40%17%2
135
December1st to 15thDay
17%9%31%33%9%
87
16th to endDay
25%6%23%25%18%1
64
January1st to 15thNight
14%218%38%21%4
720
16th to endNight
15%222%36%18%3
768
February1st to 15thNight
16%321%32%22%3
704
16th to endNight
21%316%33%21%4
632
March1st to 15thNight
10%5%16%40%22%4
720
16th to endNight
13%314%39%26%2
768
April1st to 15thNight
13%416%38%23%2
719
16th to endNight
8%5%19%33%28%4
720
May1st to 15thNight
6%317%39%32%1
609
16th to endNight
8%7%14%35%30%3
512
June1st to 15thNight
5%19%43%36%3
360
16th to endNight
343%46%5%
360
July1st to 15thNight
1120%67%8%
340
16th to endNight
11116%63%15%
479
August1st to 15thNight
1331%53%8%
717
16th to endNight
1220%60%15%
764
September1st to 15thNight
1330%51%13%
720
16th to endNight
19%34%43%10%
716
October1st to 15thNight
5%111%39%34%6%
720
16th to endNight
5%110%36%37%8%
768
November1st to 15thNight
9%210%41%30%4
760
16th to endNight
10%115%38%28%5%
780
December1st to 15thNight
14%217%40%21%4
728
16th to endNight
18%323%36%15%3
768
Page generated at 2017-12-03 08:16:46. Version ac04

Copyright 2017 A. Danko


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